1. Field of the Invention
The present invention relates to radio frequency modules (RF modules) for transmitting and receiving electromagnetic waves at radio frequencies, such as microwaves and millimeter-waves, to communication devices, and to radar devices.
2. Description of the Related Art
Generally, known RF modules for use in communication devices and radar devices include a transmission line such as a microstrip line and electronic components including an MMIC (Microwave Monolithic Integrated Circuit) and a filter on one substrate. The electronic components are connected to the transmission line using wire bonding or ribbon bonding. Such known RF modules include an oscillation circuit for oscillating an RF signal by an electronic component, a transmitter circuit for outputting a transmission signal generated by modulating the signal generated by the oscillation circuit, and a receiver circuit for demodulating a reception signal received from an antenna. In addition to these circuits, an antenna duplexer and the antenna are externally mounted.
In the above-described known RF modules, for example, the oscillation circuit, the transmitter circuit, and the receiver circuit are integrated on one substrate formed of a resin material. It is thus necessary to optically design the overall circuit in order to reduce noise. If it is necessary to modify the design of part of the RF module, such as the oscillation circuit, the entire RF module needs to be re-designed and manufactured. Not only does the RF module have poor design performance and productivity, but it is also difficult to determine the defective portion when a defective product is detected during RF module inspection.
In known RF modules, the antenna duplexer and the antenna are externally mounted and connected to each other by wire boding. Environmental changes may cause stress on the wire bonding, and the wire may be easily broken or the connection characteristics may easily change. Hence, the reliability of the RF module is low. A large transmission loss and a large return loss are caused between the RF module and the antenna duplexer, and hence the connectivity is poor.
The RF module needs to supply a large amount of transmission power to the antenna. This increases the power consumption and noise, and hence the performance of the RF module is deteriorated. Since the antenna is externally mounted, the overall device including the RF module and the antenna tends to increase in size.
Accordingly, it is an object of the present invention to provide an RF module which can be designed and manufactured separately in units of functional blocks and which is highly reliable, a communication device incorporating the RF module, and a radar device incorporating the RF module.
In order to achieve the foregoing objects, an RF module is provided including a dielectric substrate; a plurality of functional blocks provided on the dielectric substrate; and transmission lines interconnecting the functional blocks.
The dielectric substrate is formed by combining separate substrates generated by dividing the dielectric substrate into units of functional blocks. The transmission lines formed on adjacent ones of the separate substrates are electrically coupled with each other without being in contact with each other.
With this arrangement, the RF module can be designed and manufactured in units of functional blocks, and the design performance and the productivity can be improved. Since the RF module can be inspected in units of functional blocks, a defective portion (functional block) can be easily determined and exchanged. Compared with a known RF module in which transmission lines are interconnected using wire bonding, the corresponding transmission lines formed on the separate substrates are electrically coupled to each other without being in contact with each other. Thus, the stable connection characteristics can be achieved, and the reliability can be improved.
Non-contact electrical coupling means that, not only are adjacent separate substrates disconnected from each other, but also adjacent transmission lines formed on the separate substrates are not in contact with each other by wire or ribbon. Thus, a signal (RF signal) propagating through the transmission lines electromagnetically interconnects the separate substrates and is propagated.
Resonators connected to the transmission lines may be provided at edges of the separate substrates, and the resonators provided on adjacent ones of the separate substrates may be arranged close to each other and thus electromagnetically coupled to each other.
Since the resonators formed on adjacent ones of the separate substrates are electromagnetically coupled to each other, through these resonators the transmission lines can be electrically coupled to each other while not in contact with each other. Since the resonators are disposed close to each other and directly coupled to each other, the resonators can be firmly coupled to each other. Thus, low insertion loss characteristics can be achieved over a wide range of frequencies.
The plurality of functional blocks may include an antenna block for transmitting or receiving a signal; a duplexer block connected to the antenna block; a transmitter block, which is connected to the duplexer block, for outputting a transmission signal to the antenna block; a receiver block, which is connected to the duplexer block, for receiving a reception signal received by the antenna block; and an oscillator block, which is connected to the transmitter block and the receiver block, for oscillating a signal at a predetermined frequency.
Accordingly, the RF module can be re-designed and manufactured in units of functional blocks, namely, the antenna block, the duplexer block, the transmitter block, the receiver block, and the oscillator block. Since the antenna block for transmitting or receiving a signal can be included in the dielectric substrate of the RF module, the overall size of the RF module can be reduced.
The antenna block may include a parasitic antenna on a package covering the antenna block. Accordingly, the directivity and the radiation characteristics (radiation pattern) of the antenna can be adjusted using the parasitic antenna. By changing the form, size, and location of the parasitic antenna, characteristics, including the directivity, corresponding to various system specifications can be achieved. Thus, various required specifications can be satisfied.
The plurality of separate substrates may be formed by using at least two types of dielectric materials. Accordingly, the separate substrates can be formed using dielectric materials suited for the individual functional blocks. Thus, various characteristics in accordance with the individual functional blocks can be improved, and the individual functional blocks can be optimized. Also, the freedom in design can be increased.
An electromagnetic-wave absorber or a metal shielding member for preventing unwanted coupling may be provided between two adjacent ones of the separate substrates. Accordingly, unwanted coupling between adjacent separate substrates can be prevented, and noise can be reduced. In other words, unwanted waves between adjacent separate substrates are prevented from coupling with each other, and isolation can be improved. Power loss due to unwanted waves can be suppressed, and higher efficiency can be achieved.
The separate substrates may be contained in a resin package generated by metalizing a resin material. Accordingly, the surface of the metalized resin package can provide electrostatic shielding between the separate substrates and the outside, and hence external noise interference can be prevented. Compared with a case in which a metal package is used, the manufacturing cost and the weight of the overall device can be reduced.
According to other aspects of the present invention, a communication device and a radar device are provided, each including an RF module according to the present invention.